1. Field of the Invention
The present invention relates to a drum type washing machine, and more particularly, to a stator of an outer rotor type BLDC motor applicable to a direct coupling type drum type washing machine.
2. Discussion of the Related Art
Generally, a drum type washing machine performs washing operation with the aid of a drive force of a motor which spins a drum containing laundry, detergent, and water, to cause friction between laundry and water. The drum type washing machine causes almost no damage to the laundry, prevents tangling of the laundry, and brings about the effects of pounding and rubbing.
Drum type washing machines are categorized by an indirect coupling type and a direct coupling type according to a drive system. In the indirect coupling type, a drive force of a motor is indirectly transferred to a drum via a motor pulley and a belt wound to the drum pulley. In the direct coupling type, a rotor of a BLDC motor is directly coupled with a drum to directly transfer a drive force to the drum.
Yet, in the indirect coupling type system that transfers the drive force of the motor to the drum via the motor pulley and the belt wound on the drum pulley instead of transferring the drive force of the motor to the drum directly, energy loss occurs in the process of drive force transfer and considerable noise is generated.
Hence, the direct coupling drum type washing machine using the BLDC motor is widely used to solve the above problems of the drum type washing machine.
FIG. 1 is a cross-sectional diagram of a direct coupling drum type washing machine according to a related art.
Referring to FIG. 1, a tub 2 is provided within a cabinet 1, and a drum 3 is rotatably provided within the tub 2.
A motor is provided to a rear portion of the tub 2. Specifically, a stator 6 is fixed to a rear wall of the tub 2 and a rotor 5 encloses the stator 6 to be coupled to the drum 3 via a shaft.
A door 21 is provided to a front portion of the cabinet 1 and a gasket is provided between the door 21 and the tub 2.
A hanging spring 23 supporting the tub 2 is provided between an inside of a top portion of the cabinet 1 and an upper outer circumference of the tub 2, and a friction damper 24 is provided between an inside of a bottom portion of the cabinet 1 and a lower outer circumference of the tub 2 to attenuate vibration of the tub 2.
FIG. 2 is a perspective diagram of a stator in FIG. 1 and FIG. 3 is a perspective diagram of a sectional core (SC) applied to the stator in FIG. 2.
A method of manufacturing a stator core according to a related art is explained as follows.
First of all, a plurality of unit cores are fabricated by a pressing process of a steel plate. In doing so, each of the unit cores consists of teeth 151, a base portion 150, and a protrusion 500 opposite to the teeth 151 for forming a fastening hole 500a. A plurality of the unit cores are stacked to form a plurality of assemblies. And, a plurality of the assemblies are linked in a circumferential direction to complete a stator core that is so-called a stator core.
The protrusion 500 plays a role in standing a fastening force of a bolt as well as provides the fastening hole 500a necessary for securing a stator to the rear wall of the tub.
Yet, such a method of manufacturing the stator 6 with the sectional core SC is very complicated and brings about considerable loss of materials.
Meanwhile, a helical core, which is manufactured by helically stacking a steel plate consisting of teeth 151 and a base portion 150, is very useful in reducing the loss of materials and simplifying the manufacturing process. Yet, in manufacturing the helical core HC, the steel plate blanked like a strap needs to be helically bent. Hence, it is unable to provide a protrusion for coupling a stator with a tub to an inside of the core.
If the protrusion 500 is provided to the inside of the core in manufacturing the helical core HC, a core width of a part reserved for the protrusion is too large to bend the core.
Accordingly, a stator structure that enables the same role of the protrusion of the sectional core to be performed not by the core itself but by another portion is needed to be applicable to the helical core HC.
Meanwhile, it is important to sufficiently secure the rigidity of the protrusion provided with the fastening hole for securing the stator to the tub, which is explained as follows.
First of all, in a washing machine that rotates a drum directly using a BLDC motor, a stator is directly assembled to a fixing side of a rear portion of the tub. If the stator of a motor for a high capacity drum type washing machine weighs over 1.5 kg and if a dewatering rotational speed is 600˜2,000 RPM, a fastening portion of the stator 6 is broken due to the stator weight, the vibration of the high rotation, and the shake and transformation of the rotor 5.
Specifically, in case that the stator is coupled with the rear wall of the tub of the drum type washing machine using the BLDC motor, a radial direction of the stator almost maintains parallel to a ground, the breakage of the fastening portion of the stator 6 to the rear wall of the tub gets worsened due to the vibration occurring on driving the washing machine.
Therefore, it is important to sufficiently secure the rigidity of the protrusion provided with the fastening hole for securing the stator 6 to the tub.